Precious metal (Pt, Pd and Au) and Re contents in rocks, ores and flotation concentrates of Siberian (Russia) and Mongolian porphyry Cu-Mo and Mo-Cu deposits were studied. The following deposits are discussed: Early Devonian porphyry Mo-Cu Sora deposit (Kuznetsk Alatau Mountains, Russia) and porphyry Cu-Mo Aksug deposit, (northeastern Tuva, Russia); Triassic porphyry Cu-Mo Erdenetiin Ovoo deposit (northern Mongolia). The samples analyzed include unaltered host rocks of plutons, porphyry rocks of ore-bearing series, different types of altered rocks, mineral separate analyses of molybdenite, chalcopyrite and magnetite, as well as flotation concentrates. Pt, Pd, Au and Re contents were determined using ICP/MS, AAS and inversion voltammetric analysis. PGE abundances in rocks and poorly mineralized samples span a large range from below detection limit to 65 ppb Pt and 74 ppb Pd. Re concentrations in whole rock samples range from below detection limit to 89 ppb. Molybdenite has been shown to be the major host phase for Re. The results presented show that Aksug deposit reveals elevated PGE and Au contents in ore minerals and flotation concentrates. High Pd contents in ores of the Aksug deposit are in accordance with the presence of palladium mineralization in the form of palladium telluride merenskyite (Pd, Pt) Te2. The variety of precious metals and Re contents in the studied deposits could be caused by a complex interplay of several factors, including importance of primary metal concentrations derived from the source, transport of metals to the deposition area, physicochemical properties of the fluid (f02, pH, Js, T, P), and depositional conditions. Higher Re contents in molybdenite and chalcopyrite separates are typical for copper-rich Aksug and Erdenetiin Ovoo deposits. Rhenium concentration in sulfides from molybdenum-rich Sora deposit is significantly lower. Highly oxidized, Cl-rich fluid style at Aksug and Erdenetiin Ovoo was favorable for high rhenium solubility and transport to depositional area. The occurrence of significant precious metals contents at Aksug were likely due to: 1) PGE and Au enriched source, 2) favorable fluid style (high f02, high Cl-activity), promoting high solubility and transportation of precious metals in ore-forming fluid as chloride complexes; 3) moderately reducing depositional conditions from PGE-bearing solutions containing As and Te, facilitating PGM deposition. As for the porphyry systems at the Sora and Erdenetiin Ovoo deposit they were probably devoid of precursors favorable for the enrichment in PGE and Au or the role of such precursors was insignificant.
|Журнал||Acta Petrologica Sinica|
|Состояние||Опубликовано - 1 янв 2007|
ASJC Scopus subject areas
- Geochemistry and Petrology